The present invention relates to a method for immobilizing enzymes and to the product thereof as well as its uses. More particularly, the present invention relates to a method whereby enzymes are immobilized on a polyurethane foam or non-foamed substrate by means of an amino acid and/or protein bridging or coupling compound.
The use of enzymatic reactions in chemical analysis has become increasingly important in recent years, particularly with regard to the analysis of biological substances such as blood and other body fluids. Accordingly, numerous references describe the binding of enzymes using a wide number of substrates.
The use of polyurethane substrates is described in the references cited above. In U.S. Pat. No. 3,574,062 a system is described wherein a polyester polyurethane foam is used to bind enzymes via a complex procedure involving the use of amino acids and proteins. Schematically the product can be represented as follows: ##STR1##
U.S. Pat. No. 3,830,699 describes the binding of enzymes to polyacrylonitrile polymers by an intermediate reaction of the nitrile groups with an alcohol and HCl to form an imidoester followed by coupling with an enzyme. In a journal article by Lee et al. (Biochimie, 1976, 58, 489-497) enzymes are coupled to collagen using an intermediate reaction between a carbodiimide designated as EDC, i.e., 1-ethyl-3(3-dimethylaminopropyl) carbodiimide-HCl, and functional groups on the collagen surface. Subsequently, the "activated" collagen is reacted with an enzyme. The reference indicates that the procedure is applicable to numerous enzymes, e.g., hexokinase. The use of carbodiimide in binding enzymes is also described in Chemical Abstracts references 74, 19777h and 19778j wherein acrylamide-acrylic acid copolymers are reacted with a water-soluble carbodiimide followed by reaction with an aqueous enzyme solution. Enzymes employed are trypsin and a combination of hexokinase with glucose-6-phosphate dehydrogenase.